2.1.1 Basic Concepts

Representing formulae of organic compounds

In structural formulae, the carboxyl group will be represented as COOH and the ester group as COOR.
Candidates should be able to:

(a) interpret and use the terms: (i) empirical formula as the simplest whole number ratio of atoms of each element present in a compound, (ii) molecular formula as the actual number of atoms of each element in a molecule, (iii) general formula as the simplest algebraic formula of a member of a homologous series, ie for an alkane: CnH2n + 2, (iv) structural formula as the minimal detail that shows the arrangement of atoms in a molecule, eg for butane: CH3CH2CH2CH3 or CH3(CH2)2CH3, (v) displayed formula as the relative positioning of atoms and the bonds between them, ie for ethanol (vi) skeletal formula as the simplified organic
formula, shown by removing hydrogen atoms from alkyl chains, leaving just a carbon skeleton and associated functional groups, ie for butan-2-ol

Functional groups and the naming of organic compounds

(b) interpret, and use, the terms: (i) homologous series as a series of organic compounds having the same functional group but with each successive member differing by CH2, (ii) functional group as a group of atoms responsible for the characteristic reactions of a compound;
(c) use the general formula of a homologous series to predict the formula of any member of the series;
(d) state the names of the first ten members of the alkanes homologous series;
(e) use IUPAC rules of nomenclature for systematically naming organic compounds;

Isomerism

Knowledge of E/Z isomerism is restricted to understanding that this system is needed where there are more than two different substituents around the double bond, ie 1,-bromo-2-chloropropene.
Candidates are required to identify the E and Z stereoisomers in examples that also have cis and trans isomers such as but-2- ene.
E-(trans) Z-(cis)
(f) describe and explain the terms:
(i) structural isomers as compounds with the same molecular formula but different structural formulae, (ii) stereoisomers as compounds with the same structural formula but with a different arrangement in space, (iii) E/Z isomerism as an example of stereoisomerism, in terms of restricted rotation about a double bond and the requirement for two different groups to be attached to each carbon atom of the C=C group, (iv) cis-trans isomerism as a special case of EIZ isomerism in which two of the substituent groups are the same;
(g) determine the possible structural formulae and/or stereoisomers of an organic molecule, given its molecular formula;

Reaction mechanisms

Any relevant dipoles should be included.
Curly arrows should start from a bond, a lone pair of electrons or a negative charge.
(h) describe the different types of covalent bond fission: (i) homolytic fission forming two radicals, (ii) heterolytic fission forming a cation and an anion; (i) describe a ‘curly arrow’ as the movement of an electron pair, showing either breaking or formation of a covalent bond; (j) outline reaction mechanisms, using diagrams, to show clearly the movement of an electron pair with ‘curly arrows’;

Percentage yields and atom economy

Benefits to society of a high atom
economy
(k) carry out calculations to determine the percentage yield of a reaction;
(l) explain the atom economy of a reaction as: molecular mass of the desired products sum of molecular masses of all products 100%;
(m) explain that addition reactions have an atom economy of 100%, whereas substitution reactions are less efficient;
(n) carry out calculations to determine the atom economy of a reaction;

(o) describe the benefits of developing chemical processes with a high atom economy in terms of fewer waste materials;
(p) explain that a reaction may have a high percentage yield but a low atom economy.
2.1.2 Alkanes

Hydrocarbons from crude oil

Candidates should be able to:
(a) explain that a hydrocarbon is a compound of hydrogen and carbon only;
(b) explain the use of crude oil as a source of hydrocarbons, separated as fractions with different boiling points by fractional distillation, which can be used as fuels or for processing into petrochemicals;
(c) state that alkanes and cycloalkanes are saturated hydrocarbons;
(d) state and explain the tetrahedral shape around each carbon atom in alkanes

(e) explain, in terms of van der Waals’ forces, the variations in the boiling points of alkanes with different carbon-chain length and branching;

Hydrocarbons as fuels

Toxicity from CO production during
incomplete combustion of fuels.
Candidates should be aware that a catalyst is required but no detail is expected.
Desirability of renewable fuels by ‘rich’ countries may lead to problems of food supply for countries supplying the ‘crops for fuel’.
(f) describe the combustion of alkanes, leading to their use as fuels in industry, in the home and in transport;
(g) explain, using equations, the incomplete combustion of alkanes in a limited supply of oxygen and outline the potential dangers arising from production of CO in the home and from car use;
(h) describe the use of catalytic cracking to obtain more useful alkanes and alkenes;
(i) explain that the petroleum industry processes straight-chain hydrocarbons into branched alkanes and cyclic hydrocarbons to promote efficient combustion;
(j) contrast the value of fossil fuels for providing energy and raw materials with: (i) the problem of an over-reliance on nonrenewable fossil fuel reserves and the importance of developing renewable plantbased fuels, ie alcohols and biodiesel (ii) increased CO2 levels from combustion of fossil fuels leading to global warming and climate change

Substitution reactions of alkanes

Candidates are not required to use ‘half curly arrows’ in this mechanism. Equations should show which species are radicals using a single ‘dot’ to represent the unpaired electron.
(k) describe the substitution of alkanes using ultraviolet radiation, by Cl2 and by Br2, to form halogenoalkanes;
(l) define the term radical as a species with an unpaired electron;
(m) describe how homolytic fission leads to the mechanism of radical substitution in alkanes in terms of initiation, propagation and termination reactions
(n) explain the limitations of radical substitution in synthesis, arising from further substitution with formation of a mixture of products.
2.1.3 Alkenes

Properties of alkenes

Candidates should be able to:

(a) state that alkenes and cycloalkenes are unsaturated hydrocarbons;
(b) describe the overlap of adjacent p-orbitals to form a -bond;
(c) state and explain the trigonal planar shape around each carbon in the C=C of alkenes

Addition reactions of alkenes

Candidates are expected to realise that addition to an unsymmetrical alkene such as propene may result in two isomeric products. However, candidates will not be required to predict the relative proportions of these isomers, nor to apply or explain Markovnikoff’s rule.
(d) describe addition reactions of alkenes, ie by ethene and propene, with: (i) hydrogen in the presence of a suitable catalyst, ie Ni, to form alkanes, (ii) halogens to form dihalogenoalkanes, including the use of bromine to detect the presence of a double C=C bond as a test for unsaturation, (iii) hydrogen halides to form halogenoalkanes, (iv) steam in the presence of an acid catalyst to form alcohols;
(e) define an electrophile as an electron pair acceptor;
(f) describe how heterolytic fission leads to the mechanism of electrophilic addition in alkenes

Polymers from alkenes

(g) describe the addition polymerisation of alkenes;
(h) deduce the repeat unit of an addition polymer obtained from a given monomer;
(i) identify the monomer that would produce a given section of an addition polymer;

Industrial importance of alkenes

(j) outline the use of alkenes in the industrial production of organic compounds:
(i) the manufacture of margarine by catalytic hydrogenation of unsaturated vegetable
Benefits from processing of alkenes to produce polymers and plastics; drawbacks from waste polymers.
Increased political and social desire to reduce plastic waste, to recycle or to use for energy production.
Developments of new degradable plastics produced from renewable resources. oils using hydrogen and a nickel catalyst, (ii) the formation of a range of polymers using unsaturated monomer units based on the ethene molecule, ie H2C=CHCl, F2C=CF2;
(k) outline the processing of waste polymers by: (i) separation into types (ie PTFE, etc.) and recycling, (ii) combustion for energy production (iii) use as a feedstock for cracking in the production of plastics and other chemicals;
(l) outline the role of chemists in minimising environmental damage by: (i) removal of toxic waste products, ie removal of HCl formed during disposal by combustion of halogenated plastics (ie PVC), (ii) development of biodegradable and compostable polymers, ie from isoprene (2- methyl-1,3-butadiene), maize and starch

	Created by gallen96 about 10 years ago

A-Level Chemistry (F322: Module 1 - Basics and Hydrocarbons) Note on F322: Module 1 Specification, created by gallen96 on 01/04/2014.

F322: Module 1 Specification